Roller casters are widely used with a variety of furniture pieces and other loads for the convenience in moving, especially when the imparted load is large. However, in some prior art systems it was found that the rollers tend to roll randomly which may cause goods to be dropped. One prior art brake system to top the roller from rolling freely is shown in FIG. 9. The roller caster is generally composed of a main body A having a shank A1 extending upwardly therefrom. A roller B having a hole B1 along its axis is adapted to receive a shaft D therein and is secured by a pair of shaft covers C at respective ends thereof. Each shaft cover C has a protuberance C1 adapted to slide into a rail A2 formed in the inner wall of the main body A to confine movement of the cover C while the roller B is rolling. A brake block E extending from the top of the main body A engages the surface of the roller B to produce a friction force on the roller B when the brake block E is pressed downwardly. However, there are problems associated with this type of prior art system resulting from block E being accidentally released. Additionally, the brake block E may be broken if the roller caster is forced to move when it is in a locked position.